1. Field of the Invention
The present invention relates to a display device, and more particularly, to a flexible display panel.
2. Description of the Related Art
With the advancement of the flat display technology, more and more electrical products, especially portable electrical products such as mobile phones, e-books, digital cameras and personal digital assistants etc., are equipped with flat display devices. Since the portable electrical products are developed in a trend of light-weight and thin-thickness, the display devices applied to the portable electrical products must have advantages of light-weight and thin-thickness.
The flexible display panel, such as flexible electrophoretic display panel (flexible EPD panel) and flexible liquid crystal display panel (flexible LCD panel), etc., not only has features of light-weight and thin-thickness, but also has features of flexibility and hard to be broken. Thus, the development of the flexible display device has become increasingly important.
The flexible display panel generally employs a plastic substrate to replace the conventional glass substrate. However, compared with the glass substrate, the hardness of the plastic substrate is low. If employing the conventional technology of chip on glass (COG) or the technology of flexible circuit board on glass (FOG) to join the driving unit of the flexible display panel with the plastic substrate, it will produce a problem of bad reliability.
More specifically, for the anisotropic conductive film used in the conventional technology of COG or the conventional technology of FOG, the diameters of the conductive particles of the anisotropic conductive film are from 3 micrometers to 4 micrometers, and the distribution density of the conductive particles of the anisotropic conductive film is about 32000 grains per square millimeter. After replacing the glass substrate by the plastic substrate, if employing the conventional anisotropic conductive film to join the driving unit and the plastic substrate, it is prone to break the metal lines of the flexible display panel configured for being electrically connected to the driving unit, or to immerse the conductive particles into the plastic substrate. Thus, electrical contact between the driving unit and the plastic substrate is poor, and the reliability of the flexible display panel is consequently reduced.
In addition, the hot-pressing pressure of the conventional joining process for joining the driving unit and the plastic substrate is about 0.8 MPa, and the hot-pressing temperature thereof is about 210 centigrade degrees. It needs reduce the hot-pressing pressure and the hot-pressing temperature to prevent the metal lines from being broken or prevent the conductive particles from being immersed into the plastic substrate. However, reducing the hot-pressing pressure and the hot-pressing temperature cannot effectively prevent the metal lines from being broken or prevent the conductive particles from being immersed into the plastic substrate. In addition, when the pressure is reduced below 0.2 MPa, the reliability of the joining process for joining the driving unit and the plastic substrate is reduced. When the temperature is relatively low, the anisotropic conductive film may be incompletely cured.